Analysis of the behavior of Sn2+ and In3+ ions in DES and in water: a theoretical approach

Abstract

An alternative for replacing conventional organic solvents and ionic liquids, the Deep Eutectic Solvents (DES) emerged, a class of compounds with essential properties in the industry. These solvents have numerous advantages regarding ionic liquids, such as low price, biodegradability, and low toxicity. Furthermore, the DES has many applications in science, for example, organic synthesis, electrodeposition of metals, catalytic process. In this work, the behavior of Sn2+ and In3+ ions were analyzed in the solvents 1ChCl:2EG (chloride choline and ethylene glycol, DES) and water through computational simulations by molecular dynamics (MD) and Quantum Theory of Atoms in Molecules (QTAIM) calculations. The results showed that the Sn2+ and In3+ ions strongly interact with the chloride anion in DES. Furthermore, only the Sn2+ ion showed interaction with the ethylene glycol molecules in DES, which was not observed for In3+, which led to no interaction with EG. In contrast, the most likely interaction is between cations and oxygen from water in a water solvent. The analysis of Bond Critical Points (BCPs) showed that the strength of these interactions follows the following sequence: In-Ow > In-Cl > Sn-Ow > Sn-Cl. The behavior of both ions in the metallic mixture was invariant in DES and in water when compared to the same isolated ions. Furthermore, it may be observed that the increase in the number of water molecules in the systems containing water did not cause relevant changes.